Redundancy in a public safety distributed antenna system

ABSTRACT

A redundancy system for data transport in a Distributed Antenna System (DAS) includes a plurality of Digital Access Units (DAUs). Each of the plurality of DAUs is fed by a plurality of data streams and is operable to transport digital signals between others of the plurality of DAUs. The redundancy system also includes a plurality of Digital Distribution Units (DDUs). Each of the plurality of DDUs is in communication with each of the plurality of DAUs using cross connection communication paths. The redundancy system further includes a plurality of Digital Remote Units (DRUs). Each of the plurality of DRUs is in communication with each of the plurality of DDUs using cross connection communications paths.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application is a Continuation of U.S. application Ser. No.15/594,323, filed May 12, 2017, now U.S. Pat. No. 10,644,798, whichclaims priority to U.S. Provisional Patent Application No. 62/335,383,filed on May 12, 2016, entitled “Redundancy in a Public SafetyDistributed Antenna System,” each of which are incorporated by referencein their entirety for all purposes.

BACKGROUND OF THE INVENTION

Public Safety communication systems employing Distributed AntennaSystems (DAS) are available. Public Safety has stringent requirements onsystem reliability and redundancy. A DAS typically includes one or morehost units, optical fiber or other suitable transport infrastructure,and multiple remote antenna units. A radio base station is oftenemployed at the host unit location commonly known as a base stationhotel, and the DAS provides a means for distribution of the basestation's downlink and uplink signals among multiple remote antennaunits. The DAS architecture with routing of signals to and from remoteantenna units can be either fixed or reconfigurable.

A DAS is advantageous from a signal strength and throughput perspectivebecause its remote antenna units are physically close to wirelesssubscribers. The benefits of a DAS include reducing average downlinktransmit power and reducing average uplink transmit power, as well asenhancing quality of service and data throughput.

Despite the progress made in public safety communications systems, aneed exists for improved methods and systems related to public safetycommunications.

SUMMARY OF THE INVENTION

The present invention generally relates to public safety communicationsystems employing Distributed Antenna Systems (DAS) as part of adistributed wireless network. More specifically, the present inventionrelates to a DAS utilizing a software configurable network. In aparticular embodiment, the present invention has been applied to the useof cross-coupled connections amongst Digital Host Units, DigitalDistributed Units and Digital Remote Radios. The methods and systemsdescribed herein are applicable to a variety of communications systemsincluding systems utilizing various communications standards. Utilizingembodiments of the present invention, fully redundant, self-monitoring,self-healing digital DAS are provided.

Public Safety network operators face the continuing challenge ofbuilding reliable networks. Mobility and an increased level ofmultimedia content for end users typically employs end-to-end networkadaptations that support new services and the increased demand forbroadband Internet access. One of the most difficult challenges faced byPublic Safety networks is the ability to have 99.999% serviceavailability throughout the network. Fire-fighters, Police, HomelandSecurity, etc. all need guaranteed communications in the event of adisaster. A high service availability system requires full redundancy ofall elements/components on the communication path.

According to an embodiment of the present invention, a system for datatransport in a Distributed Antenna System is provided. The systemincludes a plurality of DAUs (Digital Access Units also referred to asHosts) which are connected to one or more BTSs (Base TransceiverStation). In another embodiment, the BTSs can be replaced with off-airsignals. The off-air signals could originate from BTSs wirelesslycommunicating with the DAUs or via repeaters which capture a remotesignal from a BTS. The plurality of DAUs are coupled to each other andoperable to transport signals between the plurality of DAUs. The systemalso includes a plurality of DDUs (Digital Distribution Units). Each ofthe plurality of DDUs are in communication with one or more of the DAUsusing an optical communications path. The system further includes aplurality of transmit/receive cells. Each of the plurality oftransmit/receive cells includes a plurality of DRUs (Digital RemoteUnits also referred to as Remote Units). Each of the DRUs in one of theplurality of transmit/receive cells is in communication with one or moreof the plurality of DDUs using an optical communications path (e.g., anoptical fiber, which is also referred to as an optical cable and isoperable to support both digital and analog signals (i.e., RF overfiber)).

According to another embodiment of the present invention, a system forrouting signals in a Distributed Antenna System (DAS) is provided. Thesystem includes a plurality of Base Transceiver Stations (BTS), eachhaving one or more sectors and a plurality of BTS RF connections, orDigital connections each being coupled to one of the one or moresectors. The system also includes a plurality of local DigitalDistribution Units (DDUs) located at a Local location. Each of theplurality of local DDUs is operable to route signals between theplurality of local DAUs, and coupled to at least one of the plurality ofremote DRUs. The system further includes a plurality of remote DDUslocated at a Remote location. The plurality of remote DDUs are operableto transport signals between the plurality of remote DRUs. The pluralityof local DDUs can be coupled via at least one of Ethernet cable, OpticalFiber, Microwave Line of Sight Link, Wireless Link, or Satellite Link.

The plurality of local DAUs can be connected to the plurality of remoteDDUs via at least one DWDM or CWDM signal and at least one opticalfiber. Similarly, the plurality of remote DDUs can be connected to theplurality of remote DRUs via at least one DWDM or CWDM signal and atleast one optical fiber. The plurality of remote DDUs can be coupled viaat least one of Ethernet cable, Optical Fiber, Microwave Line of SightLink, Wireless Link, or Satellite Link. In an embodiment, the pluralityof remote DDUs include one or more optical interfaces. As an example,the one or more optical interfaces can include an optical input and anoptical output. In some embodiments, the system also includes a servercoupled to each of the plurality of remote DDUs. A single DAU port isconnected to a plurality of BTSs in some implementations.

According to another embodiment of the present invention, a system forrouting signals in a DAS is provided. The system includes a plurality oflocal Digital Access Units (DAUs) located at a Local location. Theplurality of local DAUs are coupled to each other and operable to routesignals between the plurality of local DAUs. The system also includes aplurality of remote Digital Access Units (DAUs) located at a Remotelocation coupled to each other and operable to transport signals betweenthe remote DAUs and each other and a plurality of Base TransceiverStations (BTS). The system further includes a plurality of BaseTransceiver Station sector RF connections coupled to the plurality oflocal DAUs and operable to route signals between the plurality of localDAUs and the plurality of Base Transceiver Stations sector RFconnections and a plurality of DRUs connected to a plurality of remoteDAUs via at least one of a Ethernet cable, Optical Fiber, RF Cable,Microwave Line of Sight Link, Wireless Link, or Satellite Link.

According to another embodiment of the present invention, a PublicSafety system for data transport in a Distributed Antenna System (DAS)includes a plurality of Digital Access Units (DAUs), DigitalDistribution Units (DDUs) and Digital Remote Units (DRUs). The pluralityof DAUs are coupled to each other and operable to transport digitalsignals between the plurality of remote DAUs. The system also includes aplurality of Digital Distribution Units. Each of the plurality of DDUsis in communication with a plurality of DAUs using an electricalcommunications path. The system further includes a plurality oftransmit/receive cells. Each of the plurality of transmit/receive cellsincludes a plurality of DRUs. Each of the DRUs in one of the pluralityof transmit/receive cells is in communication with one of the pluralityof DDUs using an optical communications path. Redundancy of the PublicSafety system is achieve by cross connecting the optical fibers amongstthe plurality of DAU, DDU and DRUs.

Numerous benefits are achieved by way of the present invention overconventional techniques. For instance, embodiments enable the routingredundancy at the remote location. Additionally, embodiments provide forredundancy in the context of DAS-based architectures for public safetycommunication systems. These and other embodiments of the inventionalong with many of its advantages and features are described in moredetail in conjunction with the text below and attached figures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram illustrating the basic structure of a digitalaccess unit (DAU) according to an embodiment of the present invention;

FIG. 2 is a block diagram according to one embodiment of the inventionshowing the basic structure of a DAU with an integrated repeaterfunctionality on the primary and secondary inputs;

FIG. 3 is a block diagram according to one embodiment of the inventionshowing the basic structure of an integrated DAU with repeaterfunctionality on one of the inputs;

FIG. 4 is a block diagram according to one embodiment of the inventionshowing the basic structure of a digital distribution unit (DDU);

FIG. 5 is a block diagram illustrating a digital remote unit (DRU);

FIG. 6 is a block diagram illustrating the public safety systemarchitecture that ensures redundancy in the network according to anembodiment of the present invention;

FIG. 7 is a block diagram according to one embodiment of the inventionshowing the basic structure of a full redundancy Public Safety DigitalDAS architecture;

FIG. 8 is a block diagram according to one embodiment of the inventionshowing the basic structure of a full redundancy Public Safety Analog(RF over Fiber) DAS architecture;

FIG. 9 is a block diagram according to one embodiment of the inventionshowing the basic structure of the cross connection architecture fed bya base transceiver station (BTS) on the primary path and from an off-airBTS in the secondary path;

FIG. 10 is a block diagram according to one embodiment of the inventionshowing the basic structure of the cross connection architecture fed bya primary BTS and a secondary BTS; in this embodiment, a plurality ofDRUs are fed from DDU 1 and DDU 2;

FIG. 11 is a block diagram according to one embodiment of the inventionshowing the basic structure of the cross connection architecture fed bya primary off-air BTS and a secondary off-air BTS, the repeater DAU hasembedded repeater functionality;

FIG. 12 is block diagram according to one embodiment of the inventionshowing a redundant DRU in hot standby mode and connected to the primaryDRU via an optical bypass switch and RF bypass switch;

FIG. 13 is a block diagram illustrating feed and host redundancyaccording to an embodiment of the present invention;

FIG. 14 is a block diagram illustrating DDU main feed redundancy, localfeed redundancy, and aggregation of the main and local content accordingto an embodiment of the present invention;

FIG. 15 is a block diagram illustrating feed to DRU redundancy accordingto an embodiment of the present invention;

FIG. 16 is a block diagram illustrating DRU main feed redundancy, localfeed redundancy, and aggregation of a main and local content accordingto an embodiment of the present invention;

FIG. 17 is a block diagram illustrating redundancy utilizing multipleDRUs according to an embodiment of the present invention;

FIG. 18 is a simplified block diagram according to one embodiment of theinvention showing the basic structure of a full redundancy DigitalPublic Safety Digital DAS architecture;

FIG. 19 is a simplified flowchart illustrating a method for selecting aprimary or secondary feed according to an embodiment of the presentinvention; and

FIG. 20 is a block diagram illustrating uplink redundancy according toone embodiment of the present invention showing the basic structure of afull redundancy digital DAS architecture;

FIG. 21 is a block diagram illustrating DDU uplink signal redundancy toa main headend and a local headend;

FIG. 22 is a block diagram illustrating uplink signal redundancy from asingle DRU to a primary DDU, a secondary DDU and a local headend;

FIG. 23 is a block diagram illustrating uplink signal redundancy fromdual redundant DRUs to a primary DDU and a secondary DDU;

FIG. 24 is a block diagram according to one embodiment of the inventionshowing the basic structure of a full redundancy Public Safety DigitalDAS architecture; and

FIG. 25 is a block diagram according to one embodiment of the presentinvention showing the basic structure of a full redundancy digital DASarchitecture.

DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

A distributed antenna system (DAS) provides an efficient means ofutilization of base station resources. The base station or base stationsassociated with a DAS can be located in a central location and/orfacility commonly known as a base station hotel. The DAS networkcomprises one or more digital access units (DAUs) that function as theinterface between the base stations, the digital distribution units(DDUs) and the digital remote units (DRUs). The DAUs can be collocatedwith the base stations. The DRUs can be daisy chained together and/orplaced in a star configuration and provide coverage for a givengeographical area. The DRUs are typically connected via the DDUs to theDAUs by employing a high-speed optical fiber link. This approachfacilitates transport of the RF signals from the base stations to aremote location or area served by the DRUs.

FIG. 1 is a block diagram illustrating the basic structure of a localdigital access unit (DAU) 100 according to an embodiment of the presentinvention. In this embodiment, two BTSs are connected to a local DAU 100via a primary port 114 and a secondary port 116 for each band. In someembodiments, the primary port 114 and the secondary port 116 can be afirst RF input port and a second RF input port respectively. The localDAU 100 encompasses primary and secondary RF section per band thatprovide primary and secondary interface. The optical output feeds aplurality of DDUs. If the primary feed 118 or secondary feed 120 isoff-air, then an RF section with a duplexer along with a power amplifierfor the Rx path to the remote BTS and a low noise amplifier for the Txpath from the remote BTS, and multi-channel, digital, agile band-passfilters with adjustable pass bandwidth is applied for that feed asdescribed in additional detail in relation to FIG. 3.

FIG. 1 depicts a local DAU 100, also referred to as a host or host unit.In accordance with an embodiment of the present invention, each DAU isfed from a Primary BTS 102 and a Secondary BTS 104 or, as illustrated inFIG. 2, an off-air signal. An off-air signal references a wirelesssignal from a remote BTS. As an example of an off-air signal, a PrimaryBTS 102 could be located in the same building as the DAU, providing theprimary feed 118. A Secondary BTS 104 could be located remotely, forexample, several miles away from the DAU, to provide for redundancy. Inthis example, the Secondary BTS 104 would provide the secondary feed. Ifthe BTS that provides the primary feed fails, then the local DAU 100will switch to the secondary feed 120 as described more fully below. Inanother implementation, two BTSs could be collocated with the local DAU100, with one of the BTSs operating in hot standby mode. Similar use ofoff-air pickups can be implemented as discussed below.

The BTS or off-air signal is coupled to the local DAU 100 via an RFconnection or a digital connection. The local DAU 100 communicates witha plurality of Digital Distribution Units (DDUs) via an optical feed130. As illustrated in FIG. 1, the local DAU 100 can accommodatemultiple frequency bands. In some embodiments, one primary RF sectionmay be used for each frequency band.

In the embodiment illustrated in FIG. 1, the local DAU 100 includes dualRF sections: a primary RF section 106 at the 700 MHz band and asecondary RF section 108 at the 700 MHz band. These dual RF sections areutilized to receive dual inputs illustrated as the primary feed 118 andsecondary feed 120. Thus, the multi-level system redundancy provided byembodiments of the present invention includes redundancy provided byredundant RF sections in each of the DAUs.

In some cellular systems, the local DAU 100 would receive multiple bandsas appropriate for a cellular system, for example, one or more of 150MHz, 450 MHz, 700 MHz, 800 MHz, 900 MHz, etc. In some Public Safety (PS)implementations, a single band is utilized, whereas in other PSimplementations, multiple bands are utilized. As an example, FIG. 1illustrates an optional primary RF section 110 at the 800 MHz band andan optional secondary RF section 112 at the 800 MHz band. Thus, theillustrated local DAU 100 includes dual RF sections per band. Primaryand secondary feeds will be provided to the optional band(s) asappropriate.

The particular bands illustrated in FIG. 1 are not intended to limit thepresent invention but to provide exemplary bands that can be utilizedaccording to embodiments of the present invention. In this embodiment,one of the primary RF sections is designated as a primary and the otherprimary RF section is designated as a secondary. Although primary andsecondary RF sections are illustrated in FIG. 1, the present inventionis not limited to this implementation and a tertiary RF section can beutilized, as well as additional RF sections if the number of redundantsections is greater than three. One of ordinary skill in the art wouldrecognize many variations, modifications, and alternatives.

In an embodiment in which multiple bands are utilized, e.g., both 700MHz and 800 MHz bands, the feeds at these bands can be combined in a DSPunit 122. In some embodiments the DSP unit 122 can be a fieldprogrammable gate array (FPGA) configured with digital signal processinglogic. The DSP unit 122 can provide a combined digital data stream thatis output by the local DAU 100, broadcast to the DDUs 602, and thenbroadcast to the DRUs 604 as illustrated in FIG. 6. As an example, theprimary feed 118 at 700 MHz could be combined with the secondary feed126 at 800 MHz if the primary RF section 110 at 800 MHz has failed.

One feature of embodiments of the present invention is the ability toroute Base Station radio resources among the DAUs or group(s) of DAUs.In order to route radio resources available from one or more BaseStations, it is desirable to configure the individual router tables ofthe DAUs in the DAS network. This functionality is provided byembodiments of the present invention.

The DAUs are networked together as illustrated in FIG. 7 to facilitatethe routing of signals among multiple DAUs. The DAUs support thetransport of the RF downlink and RF uplink signals between the BaseStation and the various DAUs. This architecture enables the various BaseStation signals to be transported simultaneously to and from multipleDAUs. PEER ports are used for interconnecting DAUs in some embodiments.

The DAUs have the capability to control the gain (in small incrementsover a wide range) of the downlink and uplink signals that aretransported between the DAU and the base station (or base stations)connected to that DAU. This capability provides flexibility tosimultaneously control the uplink and downlink connectivity of the pathbetween a particular Remote DAU (or a group of DAUs) and a particularbase station sector.

The digital data streams 128 output by the local DAU 100 to theplurality of DDUs are the same data stream in some embodiments. Thesedigital data streams 128 enable the content to be provided to multipleDDUs for subsequent distribution to DRUs. The digital data streams 128output by the local DAU 100 can be the digital data stream based on theprimary feed 118 or the digital data stream based on the secondary feed120. The digital data stream can be output from the local DAU using atleast a first digital optical output port 130 connected to a primary DDUand a second digital optical output port 132 connected to a secondaryDDU.

In operation, both RF sections are operational. Both the primary feed118 and the secondary feed 120 are processed inside the DSP logic 122and two digital data streams are produced. The DSP unit 122 then decideswhich digital data stream will be utilized for transmission. The defaultsetting can be transmission of the primary digital data stream.Additional description related to redundant operation is provided inrelation to FIGS. 13-17.

FIG. 2 depicts a repeater Digital Access Unit (DAU) 200, also referredto as a host or host unit, which has an embedded repeater functionality.In this embodiment, two off-air feeds are connected to a repeater DAU200 via a primary port 114 and secondary port 116 for each band. The DAUwith an integrated repeater functionality encompasses a primary RFsection 206 and a secondary RF section 208 per band that provide aprimary and a secondary interface. The repeater function is provided bya duplexer 210 along with a power amplifier 214 for the Rx path to theprimary remote BTS 202 and a low noise amplifier 212 for the Tx pathfrom the remote BTS, and multi-channel, digital, agile band-pass filterswith adjustable pass bandwidth. If the primary or secondary feed is froma collocated Base Station, then an RF section without a duplexer, poweramplifier for the Rx path, and low noise amplifier for the Tx path isapplied for that feed as described in additional detail in relation toFIG. 3.

In accordance with embodiments of the present invention, each repeaterDAU 200 is fed from a Primary remote BTS 202 and a secondary Remote BTS204. The BTS or off-air signal is coupled to the DAU via an RFconnection or a digital connection. The repeater DAU 200 has an embeddedduplexer 210, Low Noise Amplifier 212 and Power Amplifier 214. Thisfacilitates the communication with remote BTSs or an off-air signalsource over large distances in which signals are weaker than fromcollocated BTSs. If the mixed signal feeds are delivered to a DAU, localBase Station and off-air (remote Base Station), two types of RF sectionsare implemented.

FIG. 3 depicts a Digital Access Unit (DAU) 300, also referred to as ahost or host unit, operable to receive mixed signals. In thisembodiment, mixed signal feeds are delivered to a DAU—Primary BaseStation 102 and off-air (remote Base Station) 204 feeds are connected toan integrated DAU 300 via a primary port 114 and secondary port 116 foreach band. The integrated DAU 300 encompasses a primary RF section 106and a secondary RF section 208 per band, that provide primary andsecondary interfaces. The optical output 130 feeds a plurality of DDUs.For the remote BTS 204 feed RF section 208 with a duplexer 210 alongwith a power amplifier 214 for the Rx path to the remote BTS 204 and alow noise amplifier 212 for the Tx path from the remote BTS 204, andmulti-channel, digital, agile band-pass filters with adjustable passbandwidth is applied. For feed from a collocated Base Station 102 RFsection 106 without a duplexer, power amplifier for the Rx path, and lownoise amplifier for the Tx path is applied.

In this embodiment, for the off-air feed/secondary remote BTS 204, an RFsection 208 with a duplexer 210, power amplifier 214, and low noiseamplifier 212 is used, while for the feed from a collocated BaseStation, an RF section 106 without a duplexer, power amplifier, and lownoise amplifier is used. The integrated DAU 300 communicates with aplurality of Digital Distribution Units (DDUs) via an optical feed 130.As illustrated in FIG. 2, the repeater DAU 200 can accommodate multiplefrequency bands. In some implementations, the repeater functionality canbe provided separately, although this repeater functionality isillustrated as embedded in FIGS. 2 and 3.

FIG. 4 depicts a Digital Distribution Unit (DDU) 400. The DDU 400 routesoptical signals between the plurality of DAUs and a plurality of DRUs.In accordance with the present invention, each DDU 400 is fed from aPrimary DAU 402 and Secondary DAU 404. The DDU 400 is coupled to theplurality of DAUs via optical connections 406. The DDU 400 communicateswith a plurality of Digital Remote Units (DRUs) via an optical feed. Asillustrated in FIG. 3, the DDU 400 can accommodate interfacing tomultiple primary and secondary DAUs. The DDU 400 distributes the BTS orOff-air signals to a plurality of DRUs.

The DDU 400 receives the primary data stream 418 and the secondary datastream 420 from the redundant set of the primary DAU 402 and thesecondary DAU 404 and redistributes signals based on either or both ofthe primary data stream 418 and the secondary data stream 420 to anetwork of DRUs. As illustrated in FIG. 4, the primary data stream 418is received from a primary DAU 402 in the Main Headend 410. A firstinput port 430 is coupled to the first digital optical output port ofthe primary DAU 402. The secondary data stream 420 is received from asecondary DAU 404 in the Main Headend 412. A second input port 432 iscoupled to the first digital optical output port of the secondary DAU404.

As illustrated in FIG. 4, the DDU 400 provides a larger number ofoptical outputs 408 for delivery of data streams 428 to the DRUs thanthe number of data streams received at the DDU 400. This enables asystem architecture in which a small number of DAUs and DDUsinteroperate with a large number of DRUs. The DDU 400 receives the datastream from the DAU and redistributes the data stream to multiple DRUs.In some embodiments, the DDU 400 has 16 optical ports 414, with twoutilized to receive the primary data stream 418 and the secondary datastream 420 and 14 utilized as output ports to provide data streams tothe DRUs. At least a first output port and a second output port of theoptical ports 414 are utilized to provide redundancy for the datastreams to the DRUs. In other embodiments, including the embodimentillustrated in FIG. 4, two optical ports are utilized to receive theprimary data stream 418 and the secondary data stream 420 from the MainHeadend 410. Further, two optical ports are utilized to receive theLocal Headend primary local data stream 422 and the Local Headendsecondary local data stream 424 from the Local Headend, with 12 opticalports utilized to provide data streams 128 to the DRUs.

In the illustrated embodiment, the Local Headend 412 can represent alocal municipality service that operates on the same or a different bandthan the entity represented by the Main Headend 410. The DAUs at theLocal Headend 412 can provide additional data streams that can bereceived by the DDU 400, aggregated with the data stream received fromthe Main Headend 410, and delivered to the DRUs. As an example, theprimary data stream 418 from the Main Headend and the primary datastream 422 from the Local Headend could be processed in a DSP unit 430.In some embodiments, the DSP unit 430 can be an FPGA configured withdigital signal processing logic. The DSP unit 430 can generate acombined stream and the combined stream can be transmitted to the DRUs.In addition to distribution or rebroadcasting of a data stream from asmall number of DAUs, or host units, to a larger number of DRUs, the DDU400 can aggregate additional data streams locally at the location whereit is positioned, thereby providing augmentation of services for aparticular area.

FIG. 5 depicts a Digital Remote Unit (DRU) 500 which contains a 700 MHzband RF section 502 and an 800 MHz band RF section 504 that deliver theBTS Tx signal 506 to the antenna and receives the User Rx signal 508from the antenna, according to an embodiment of the present invention.The DRU 500 is interconnected with a plurality of DDUs. The DRU 500translates the RF Rx signals to digital signals for transport to the BTSand translates the digital Tx signals from the BTS to RF signals forbroadcasting over the antenna. In accordance with the present invention,each DRU 500 is fed from a Primary DDU 510 and a Secondary DDU 512. TheDRU 500 is coupled to the plurality of DDUs via optical connections 514.As illustrated in FIG. 5, the DRU 500 can accommodate interfacing tomultiple frequency band RF transceivers. The DRU 500 consists of aplurality of RF sections and a multiplexer 516 to facilitateinterconnection 518 to a RF antenna.

The DRU 500 receives a primary data stream 520 and a secondary datastream 522 from the Primary DDU 510 and the Secondary DDU 512. In FIG.6, for example, DDU-1 and DDU-3 in TD 1 612 provide the primary datastream 520 and the secondary data stream 522 to DRU-T1. A DSP unit 524processes the received data streams to provide outputs to the RFsection(s), which can be implemented at different bands as needed toprovide the RF output for the leaky coaxial cable, for example, in atunnel, or a station antenna, either directional or omnidirectional. Insome embodiments, the DSP unit 524 can be an FPGA configured withdigital signal processing logic.

FIG. 6 depicts one embodiment of a Public Safety system architecture600. The plurality of DAUs 602 feed a plurality of DDUs 604 that in turnfeed a plurality of DRUs 606 (which can also be referred to as remoteunits). In accordance with the present invention, a plurality of DAUs602 are interconnected with a plurality of DDUs 604 that feed aplurality of DRUs 606. As illustrated in FIG. 6, at RF Headend 1 608there is a collocated a primary and secondary DAUs 610. Similarly at TD1 612 there is collocated a primary and secondary DDU 614. The primaryand secondary DDUs feed a plurality of DRUs 606. The DRUs 606 areconnected to antennas 616 that provide coverage to a fixed remotelocation.

The system illustrated in FIG. 6 includes 3 RF Headend sites, 6 TunnelDistribution (TD) sites, and Station Distribution (SD) equipment. Inthis configuration, 126 DRUs for tunnels coverage and 56 DRUs forstation coverage are utilized. It should be noted that TD and SDequipment can be integrated with Headend sites. As illustrated, the unitcount is redundant DAUs: 8; Digital Distribution Units: 32; and DRUs:182.

The 3 RF Headend sites are fed by different base station resources.Referring to RF Headend 1 608, a pair of redundant DAUs 610 arerepresented by Host-1 and Host-2. The pair of redundant DAUs 610provides a data stream 618 to multiple, redundant DDUs 614, which arealso arranged in pairs. Each pair of redundant DDUs 614 provides thedata stream 618 to multiple DRUs. Thus, the single line between Host-1and DDU-1 620 represents a set of four redundant lines connecting DAU-1and DAU-2 to DDU-1 and DDU-2. The single line between DDU-1 and DDU-2 toDRU-T1 622 represents a set of two redundant lines connecting DDU-1 andDDU-2 to DRU-T1. Thus, the optical fibers illustrated in FIG. 6 areexemplary and simplified and not intended to limit the number ofconnections provided between elements. In this implementation, TD 1 612includes DDU1-DDU-4, TD 2 includes DDU-5-DDU-8, and the like. In FIG. 6,the set of DDUs, DDU-1 and DDU-2 feed DRU-T1-DRU-T14. The other TunnelDistribution sites TD 2 through TD 24 provide data streams to DRU-T15through DRU-T126.

FIG. 7 depicts a Digital Public Safety system 700 that includes multiplecross connections between DAUs, DDUs and DRUs. The primary feed 118 andsecondary feed 120 are networked via a cross connection between the DAUs706, a cross connection between the DDUs 708 (DDU16) and a crossconnection between the DRUs 710 (hd37 s). Redundancy in coverage isachieved by overlapping antenna radiation patterns 712. The secondaryunits/elements 716 work in parallel, so that should any of the primaryunits/elements 714 fail, secondary units/elements 716 are ready to carryon the task with a minimum switchover time. Performance of the primaryunits/elements 714 and the secondary units/elements 716 is monitored andinformation is used by decision-making logic to automaticallyreconfigure system units/elements, if failure is detected. Crossconnection between system units/elements provide an operational systemresilient to simultaneous multi-point failures. As described more fullybelow, embodiments of the present invention provide redundancy atseveral levels, including multiple, redundant DAUs at the Main Headend718, multiple, redundant RF sections in each DAU, multiple, redundantDDUs at the Secondary Headend 720, and the like.

Referring to FIG. 7, in the illustrated embodiment, the primary feed 118and secondary feed 120 are split between multiple DAUs. As discussed inrelation to FIG. 1, the primary DAU 722 and the secondary DAU 724 haveredundant RF sections (for each band served), that enable reception ofthe primary feed 118 and the secondary feed 120 by the DAUs. The primaryDAU 722 and the secondary DAU 724 are cross connected by crossconnection 706 at the digital/baseband level. The primary DAU 722provides content in a form of data stream to the secondary DAU 724, andsecondary DAU 724 provides content to the primary DAU. The primary DAU722 and the secondary DAU 724 are cross connected 708 to a primary DDU726 and a secondary DDU 728 as depicted in FIG. 7. The primary DDU 726and the secondary DDU 728 are also use a cross connection between theDRUs 710, DRU-1 730 and a second DRU-2 732. The DRUs achieve redundancyby having overlapping antenna radiation patterns 712 with other DRUs.

The high service availability is achieved by 1:1 redundancy, which canalso be considered as dual modular redundancy. Each element in thenetwork (except DRU) has a secondary unit. Secondary units/elements 716work in parallel, so that should any of the primary units/elements 714fail, secondary unit(s) is/are ready to carry on the task with a minimumor reduced switchover time. Performance of the primary units/elements714 and the secondary units/elements 716 is monitored and informationused by decision making logic to automatically reconfigure systemunits/elements, if failure is detected. Cross connection between systemunits/network elements provide operational systems resilient tosimultaneous multi-point failures. Some embodiments of the presentinvention provide system availability of up to and exceeding 99.999%availability, for example, in an implementation for 700 MHz RadioSystems.

As illustrated in FIG. 7, the primary DAU 722 receives, at the primaryRF section (RF-P), the primary feed 118 from the splitter/combiner 734.The primary DAU 722 also receives, at the secondary RF section (RF-S),the secondary feed 120 from a second splitter/combiner 736. Thesplitter/combiner 734 and the second splitter/combiner 736 enable theprimary feed 118 and the secondary feed 120 to be received at both theprimary DAU 722 and the secondary DAU 724. Both the primary feed 118 andthe secondary feed 120 are processed in by a DSP unit in each of theDAUs. A first DSP unit 723 in the primary DAU 722 generates a primarydata stream 738 and a second DSP unit 725 in the secondary DAU 724generates a secondary data stream 740 and either the primary data stream738 or the secondary data stream 740 is selected as discussed herein. Inbetween the Main Headend 718 and the Secondary Headend 720, as well asbetween the Secondary Headend 720 and the Tunnel/Station Distribution742, multiple optical fibers can carry either the primary feed 118 orthe secondary feed 720 depending on whether the primary feed 118 or thesecondary feed 120 is selected by the first DSP unit 723 in the primaryDAU 722 and the second DSP unit 725 in the secondary DAU 724.

Cross connection 706 of the DAUs at the digital level is provided asillustrated in FIG. 7. The first DSP unit 723 in the primary DAU 722 isconnected to the second DSP unit 725 in the secondary DAU 724 and viceversa. The connection of the first DSP unit 723 and the second DSP unit725 enables operation in the event of failure of both RF sections in oneof the DAUs. As discussed in additional detail in relation to FIG. 13,if both RF sections in the primary DAU 722 fail, the primary feed 118 orsecondary feed 120 received at the secondary DAU 724 can be delivered tothe first DSP unit 723 of the primary DAU 722 through the crossconnection 706 between the first DSP unit 723 and the second DSP unit725. As a result, failure of both RF sections in one of the DAUs can becompensated for through the cross connection 706 at the DSP unit level.

Referring to FIGS. 7 and 13, the cross connection 706 is implemented, inan embodiment, by connections from the primary DAU 722 to the secondaryDAU 724 and from the secondary DAU 724 to the primary DAU 722. Asdescribed herein, these are digital connections between the FPGA/DSPsections of the DAUs. Referring to FIG. 13, the connection between thefirst DAU and the second DAU is provided by primary data stream 1334from the primary integrated DAU 1302 that is received by ASP2 1333 inthe second integrated DAU 1304. The connection between the second DAUand the first DAU is provided by secondary data stream 1336 from thesecondary integrated DAU 1304 that is received by ASP2 1332 in the firstintegrated DAU 1302.

Fiber redundancy between the Main Headend 718 and the Secondary Headend720 is provided by embodiments of the present invention as illustratedin FIG. 7. For example, the primary DAU 722 outputs the primary datastream 738. The primary DAU 722 can include a first digital opticaloutput port connected to a first input port on the primary DDU 726 and asecond digital optical output port connected to a first input port onthe secondary DDU 728. The secondary DAU 724 outputs the secondary datastream 740. The secondary DAU can include a first digital optical outputport connected to a second input port on the primary DDU 726 and asecond digital optical output port connected to a second input port onthe secondary DDU 728. In the example configuration, the output fromeach DAU is transmitted on two fibers, one fiber connects a DAU to theprimary DDU 726 and a second fiber connects the DAU to the secondary DDU728. In a default mode, for example no failures, the primary feed 118 isprocessed by the primary DAU 722 and the secondary DAU 724 and theprimary data stream 738 and secondary data stream 740 both transmit dataassociated with the primary feed 118 providing redundancy for theprimary feed 118. In the default mode both DDUs then transmit theprimary data stream 738 to the DRUs.

If one of the primary RF sections fails in a DAU, the DSP unitassociated with the failed RF section can switch to provide thesecondary feed 120 generated from the secondary RF section as the datastream. In the example embodiment, if the primary DDU 726 receives aprimary data stream 738 and a secondary data stream 740 with differentfeeds, the logic in the DSP unit 727 of the primary DDU 726 can beconfigured to select a data stream to transmit to the DRUs based on oneor more signal characteristics.

In FIG. 7, the dots below the DDUs 746 in the Secondary Headend and thedots below the DRUs 744 represent implementations in which additionalDDUs and additional DRUs are utilized. Examples of such implementationswere discussed previously in relation to FIG. 6. Examples would includeimplementations in which additional DRUs are provided in tunnels,additional bands are utilized, and the like. One of ordinary skill inthe art would recognize many variations, modifications, andalternatives.

In the system illustrated in FIG. 7, the set of DRUs, DRU-1 730 andDRU-2 732, receive redundant digital data streams from the primary DDU726 and the secondary DDU 728 using cross connection between the DRUs710. DRU-1 730 includes a first input port coupled to a first outputport of the primary DDU 726 and a second input port coupled to the firstoutput port of the secondary DDU 728. DRU-2 732 includes a first inputport coupled to a second output port of the primary DDU 726 and a secondinput port coupled to the second output port of the secondary DDU 728.DRU-1 730 and DRU-2 732 process the digital data streams and provide RFsignals using an RF output port to antennas A1 and A2 respectively. A1and A2 are arranged such that their antenna coverage areas produceoverlapping antenna radiation patterns 712. Thus, redundancy is achievedthrough overlapping coverage, which enables the system cost to bereduced (for systems in which the number of remote units is much greaterthan the number of hosts and distribution units) in comparison withsystems that would utilize redundant remotes. If one of the DRUs fails,then coverage in the area covered by the failed DRU will be provided bythe other DRU.

FIG. 24 is a block diagram according to one embodiment of the inventionshowing the basic structure of a full redundancy Public Safety DigitalDAS architecture. FIG. 24 illustrates a system 2400 configured tointerface directly with a primary backhaul connection 2402 and asecondary backhaul connection 2404. The system 2400 includes many of thefeatures described in relation to FIG. 7 that provide redundancy in adigital public safety system including cross connections between theDAUs, DDUs, and DRUs. Accordingly, the discussion provided in relationto FIG. 7 is applicable to the system illustrated in FIG. 24 asappropriate. System 2400 replaces the primary DAU and the secondary DAUwith a primary baseband unit (BBU) 2406 and a secondary BBU 2408. EachBBU includes a microprocessor section 2410 and a DSP unit 2412 toprocess the signals required to interface with the DDUs in the secondaryheadend 720 and the backhaul connections. The BBUs at the main headend2410 include output ports that connect to the input ports on the DDUs atthe secondary headend 720. In some implementations, the BBU/DDUinterface may use a standard such as OBSAI (Open Base StationArchitecture Initiative), CPRI (Common Public Radio Interface) and/orORI (Open Radio Interface).

FIG. 8 depicts an Analog Public Safety system that includes multiplecross connections between Main Hubs, Secondary Hubs and Remote Units(RUs). The primary feed 118 and secondary feed 120 are networked via across connection 802 between the main Hubs, a second cross connection804 between the Expansion Hubs and a third cross connection 806 betweenthe RUs (Remote Units). Redundancy in coverage is achieved byoverlapping antenna radiation patterns 712. The secondary units/elements816 work in parallel, so that should any of the primary units/elements814 fail, secondary unit(s) is/are ready to carry on the task with aminimum switchover time. Performance of the primary and secondaryunits/elements is monitored and this information is used bydecision-making logic to automatically reconfigure systemunits/elements, if failure is detected. Cross connection between systemunits/elements provide operational systems resilient to simultaneousmulti-point failures. As described more fully below, embodiments of thepresent invention provide redundancy at several levels, includingmultiple, redundant Main Hubs at the Main Headend 718, multiple,redundant RF sections 848 and Optical Modules 850 in each Main Hub,multiple, redundant Expansion Hubs at the Secondary Headend 720,multiple, redundant Optical modules 850 and Remote Unit Drive modules852 in each Secondary Hub, and the like.

Referring to FIG. 8, in the illustrated embodiment, the primary feed 118and the secondary feed 120 are split between multiple Main Hubs. Theprimary main hub 822 and the secondary Main Hub 824 have redundant RFsections 848 (for each band served), that enable reception of theprimary feed 118 and the secondary feed 120 by the Main Hubs. Theprimary main hub 822 and the secondary Main Hub 824 are cross connected804 to a primary expansion hub 826 and a secondary expansion Hub 828over primary and secondary Optical Modules 850, as depicted in FIG. 8.The primary expansion hub 826 and the secondary expansion Hub 828 arealso cross connected 806 to multiple RUs, RU-A1 830 and RU-A2 832, overprimary and secondary Remote Unit Drive modules 852 in the ExpansionHubs and primary and secondary optical section 854 in the RU-A1 830. Inanother embodiment, the RU-A2 832 optical front end is comprised of anoptical switch 856 that performs selection between primary and secondaryoptical signals, and an optical section 854 that transfers the opticalsignal back to RF. The RUs achieve redundancy by having overlappingantenna radiation patterns 712 with other RUs.

FIG. 9 depicts a Public Safety System 900 that is fed by a combinationof a Local BTS 902 and a remote BTS 904. The remote BTS 904 is thesecondary feed 120 for the Public Safety architecture. Theinterconnection between the DAUs and the DDUs 924 as well as between theDDUs 924 and the DRUs 926 demonstrates the 1:1 redundancy of the system900. To better illustrate the redundancy capability; any failure ofeither a BTS, a RF connection, a fiber, a DAU, a DDU or a DRU will beaccommodated by re-routing the signals through alternative paths.

Referring to FIG. 9, redundancy of the feed is provided by a primaryfeed 118 from the above ground base station 902 and an off-air secondaryfeed 120 from the above ground tower 906. Redundancy of the host units,for example DAUs, each with redundant RF sections, and cross connectionat the digital level 908 is provided in the RF Headend 1 910. TD-1 912provides a set of redundant distribution units fed with dual fiber link,thereby providing fiber link redundancy. Redundancy at the remotelocations is provided by DRUs fed with dual fiber link, addingadditional fiber link redundancy.

Referring to FIG. 9, two different feeds are utilized for the primaryfeed 118 and the secondary feed 120: a base station 902 feed and off-airdirectional antenna 914 pickup from a macro tower 906. Because of thediffering nature of the feeds, different types of RF sections areutilized as illustrated in the integrated DAU 300 in FIG. 3. The DSPs ofthe primary integrated DAU 916 and the secondary integrated DAU 918 areinterconnected as discussed in relation to FIG. 7.

Primary and secondary optical fibers 920 carry the data streams from theprimary integrated DAU 916 and the secondary integrated DAU 920 in theRF Headend 1 910 to the DDUs in the secondary headend TD-1 912. In thisimplementation, the primary optical fibers 922 from the primaryintegrated DAU 916 connect to four DDUs 924 in TD-1 912. The DDUs 924then replicate the data streams and deliver or rebroadcast them to the28 DRUs 926.

In the embodiment illustrated in FIG. 9, the secondary feed 120 isprovided to the primary integrated DAU 916 and the secondary integratedDAU 918. Due to the mixed signal type feed in this embodiment (e.g.,from the Base station and/or from off-air) the Host unit will have twotypes of RF modules. As illustrated in FIG. 3, for the off-air feed, theintegrated DAU unit will have an RF module with a power amplifier and alow noise amplifier. For the Base Station feed, the integrated DAU unitwill have an RF module without the PA and LNA.

FIG. 10 depicts a Public Safety System 1000 that is fed by a combinationof two Local BTSs. The secondary BTS 1002 is in hot swappable standbymode. Redundancy is provided at the base station level (set of redundantBTSs 1002, 1004), at the Headend 1010 level (set of redundant hostunits, primary DAU 1006 and DAU 1008, each with redundant RF sectionsand cross connection at the digital level), at the secondary headend1012 level (redundant distribution units, DDU 924, fed with dual fiberlink=>fiber link redundancy), and at the remote level (DRU 926, fed withdual fiber link=>fiber link redundancy). Since the feeds are providedfrom base stations, the host units can both be a local DAU 100 asillustrated in FIG. 1.

FIG. 11 depicts a Public Safety System 1100 that is fed by off-airsignals 1102 from a combination of two remote BTSs. Redundancy isprovided in a manner similar to that discussed in relation to FIG. 10.Redundant donor directional antennas 1104 pointing to different donorsites receive RF signals. Redundant host units 1106, 1108 as illustratedby repeater DAU 200 in FIG. 2, each with redundant RF sections, andcross connection at digital level, receive the RF signals and utilizethe integrated repeater function to amplify the received RF signals.Redundant distribution units, DDU 924, fed with dual fiber link providefiber link redundancy. Redundancy at the remote units, DRU 926, isprovided by feeding the remote units with a dual fiber link to provideadditional fiber link redundancy.

FIG. 12 depicts a Public Safety System 1200 utilizing a primary DRU 1202and hot swappable secondary DRU 1204. In the redundant systemillustrated in FIG. 7, each of the system elements is implemented in aredundant manner: Main Headend with redundant hosts; Secondary Headendwith redundant DDUs; and Tunnel/Station Distribution with DRUs havingoverlapping coverage areas to provide redundancy at the DRUs. FIG. 12illustrates another possible implementation in which, rather thanutilizing overlapping coverage areas, a redundant secondary DRU 1204 isutilized at the remote level to provide redundancy.

In the embodiment illustrated in FIG. 12, redundancy is provided insituations, for example, applications that emphasize backup protection,in which the benefit provided by redundant DRUs outweighs the additionalsystem cost associated with the redundant DRUs. In this implementation,1:1 redundancy is provided in a hot standby mode. In default operation,the secondary DRU 1204 is active, but it is not processing the signalreceived by the primary DRU 1202. Additional description of thisoperation is provided in relation to FIG. 17.

According to embodiments of the present invention, architecturesincluding a variation of a Dual Modular Redundancy (DMR) are utilized inwhich duplicated elements work in parallel, so that should any of thesystem elements/components fail, another element/component is ready tocarry on system tasks with a reduced or minimum switchover time.Embodiments of the present invention utilize Active Redundancy systemsin which performance of the key elements is monitored and information isused by decision-making logic to automatically reconfigure the systemcomponents if failure is detected.

FIG. 13 is a block diagram of a public safety system 1300 illustratingfeed and host redundancy according to an embodiment of the presentinvention. The primary feed 118 and secondary feed 120 are delivered tothe primary integrated DAU 1302 and the secondary integrated DAU 1304via a splitter/combiner 1306 such that they are fed to a redundant RFsection 1308 in the primary integrated DAU 1302 and a second redundantRF section 1310 in the secondary integrated DAU 1304. As illustrated inFIG. 13, both primary integrated DAU 1302 and secondary integrated DAU1304 have both primary and secondary RF sections at one or more bands(e.g., 700 band and 800 band). In some embodiments, the primaryintegrated DAU 1302 and/or the secondary integrated DAU 1304 arequad-band units, providing primary and secondary RF sections at twobands. Thus, the primary feed 118 is provided to primary RF section 1320and secondary RF section 1313 and the secondary feed 120 is provided toprimary RF section 1311 and secondary RF section 1322. Both of theprimary feed 118 and secondary feed 120 are translated into the digitaldomain and processed inside the DSP Unit 1312 in each of the DAUs. Theprimary integrated DAU 1302 utilizes the digital signal processingfunctionality provided by the DSP Unit 1312 to implement two decisionpoints: monitoring and/or selection of primary feed 118 or secondaryfeed 120 provided by the primary BTS 1314 or the secondary source 1316,and monitoring and/or selection of a primary/secondary feed from thesecondary integrated DAU 1304 received over a fiber connecting the DAUs1318 (e.g., the secondary integrated DAU 1304) in case the primary feed118 or the secondary feed 120 is not available due to primary hostfailure. One of skill in the art will understand that the fiberconnecting the DAUs 1318 corresponds to cross connection 706 in FIG. 7.

In default operation, considering the primary host (primary integratedDAU 1302), both the primary feed 118 processed by the primary RF section1320 and the secondary feed 120 processed by the secondary RF section1322 are converted to digitals signals using the ADCs 1324 and presentedto Automated Selection Point 1 a (ASP1 a) 1326. The switch representedby the logic implementing ASP1 a 1326 is set such that the digitalsignal associated with the primary feed 118 is passed through ASP1 a1326 by default. The digital signal passed by ASP1 a 1326 is thencombined with the optional digital signal passed through a second ASP1 b1328 receiving digital signals at the optional 800 MHz band. Thus, ASP1logic is provided for each band that is implemented in the hosts.

A splitter 1330 is utilized to provide a copy of the combined signal,local data stream 1334, to Automated Selection Point 2 (ASP2) 1333 ofthe secondary integrated DAU 1304. If the combined signal provided byASP2 1332 of the primary integrated DAU 1302 is suitable for broadcast,the switch represented by the logic implementing ASP2 1332 passes thecombined signal for delivery to the DDUs. Similar operation is carriedout concurrently or simultaneously in the secondary integrated DAU 1304,which also receives the primary feed 118 and the secondary feed 120.Modifications from default operation are also provided by embodiments ofthe present invention.

At the first decision point, an Automated Selection Point 1 a (ASP1 a)1326 passes the primary feed 118 (signal) or switches to the secondaryfeed 120 (signal) output by the secondary RF section 1322 if loss ofprimary feed 118 (signal) is detected (e.g., which could result fromprimary BTS 1314 or primary RF section 1320 failure). Thus, measurementsof the digital signals output by the ADCs 1324 coupled to each of theprimary RF section 1320 and the secondary RF section 1322 made at theASP1 a 1326 enable ASP1 a 1326 to pass the primary feed 118 (signal) asa default or switch to the secondary feed 120 (signal) if the quality ofthe primary feed 118 (signal) is below a threshold. Thus, if theperformance of the primary feed is below a threshold, then ASP1 a canswitch to the secondary feed, which can then be passed to splitter 1330.

At the second decision point, a second Automated Selection Point (ASP2)1332 passes the local data stream 1334 or switches to an external datastream 1336 provided by a secondary host (secondary integrated DAU 1304)if loss of the local data stream 1334 is detected (e.g., which couldresult, for instance, from both RF sections or ADC/DAC circuit failure).In an embodiment, ASP2 1332 will pass the local data stream 1334 as adefault.

In an embodiment, if failure (e.g., performance below a threshold) ofboth primary RF section 1320 and second RF section 1322 occurs,resulting in loss of output from ASP1 a 1326 (assuming no signal at thesecond band), no signal will be received at splitter 1330. In thisembodiment, ASP2 1332 will thus select the external data stream 1336 forrebroadcasting if the quality of the local data stream 1334 is below athreshold. The external data stream 1336 is an output of ASP1 a 1327 inthe secondary integrated DAU 1304. Thus, digital content from thesecondary integrated DAU 1304 is delivered as external data stream 1336to ASP2 1332 in the primary integrated DAU 1302, and, in turn, toprimary fibers 1338. The primary fibers are connected to one or moredigital optical output ports 1348. The one or more digital opticaloutput ports include a first digital optical output port connected to aprimary DDU and a second digital optical output port connected to asecondary DDU.

Accordingly, digital cross connection between the RF sections of theDAUs is provided by embodiments as previously discussed in relation toFIG. 7. As a result, the system 1300 is able to maintain the signal onboth the primary fibers 1338 and secondary fibers 1340 to the primaryand secondary DDUs respectively. Thus, embodiments of the presentinvention enable operational signals on either or both primary fibers1338 and secondary fibers 1340 to be maintained, even in the event offailure of the RF sections and/or DSP unit in either the primaryintegrated DAU 1302 or the secondary integrated DAU 1304. In someimplementations, the ASP1 a 1326 or ASP1 b 1328 or ASP2 1332 switchingtime is less than a few seconds, for example, less than 2 sec.

In FIG. 13, the 800 MHz band is illustrated as optional. If the 800 MHzband is utilized, the DSP unit 1312 receives primary and secondary datastreams for both bands from the primary and secondary RF sectionsassociated with each band. In the illustrated embodiment, the DSP unit1312 receives a primary 800 MHz data stream 1342 and a secondary 800 MHzdata stream 1344. The 800 MHz band includes the second AutomatedSelection Point 1 (ASP1 b) 1328 that passes the primary 800 MHz datastream 1342 or switches to the secondary 800 MHz data stream 1344 outputby the secondary RF section 1346 if loss of the primary data stream 1342at the 800 MHz band is detected. Data streams representing differentbands are aggregated and then delivered to the second AutomatedSelection Point (ASP2) 1332 that passes the local data stream 1334 orswitches to an external data stream 1336 provided by a secondary host(secondary integrated DAU 1304) if loss of the local data stream 1334 isdetected.

In both the primary integrated DAU 1302 and the secondary integrated DAU1304, the primary and secondary streams are provided to the DSP unit1312. If the primary integrated DAU 1302 fails such that the redundantRF section 1308 has failed and the primary integrated DAU 1302 losesboth data streams, the system 1300 can provide self-healing. The system1300 can use the data stream produced by the DSP unit 1312 in thesecondary integrated DAU 1304 (e.g., the primary RF Section data stream)and can deliver this data stream to the DSP unit 1312 in the primaryintegrated DAU 1302. The system can transmit the data stream to theprimary DDUs after passing the data stream through ASP2 1332 in the DSPunit 1312 in the primary integrated DAU 1302. The same data stream willbe provided by the second integrated DAU 1304 to the secondary DDUs.Accordingly, both the primary and secondary data streams can bemaintained on the fiber connecting the DAUs 1318 (Main Headend) and theDDU units (Secondary Headend). If the primary data stream is produced bythe DSP unit 1312 in the secondary integrated DAU 1304, then thisprimary data stream is provided to the DSP unit 1312 in the primaryintegrated DAU 1302 for transmission to the Secondary Headend. If thesecondary data stream is produced by the DSP unit 1312 in the secondaryintegrated DAU 1304, then this secondary data stream is provided to theDSP unit 1312 in the primary integrated DAU 1302 for transmission to theSecondary Headend. It should be noted that the discussion provided inrelation to the operation of primary integrated DAU 1302 is applicableto secondary integrated DAU 1304 as appropriate. One of ordinary skillin the art would recognize many variations, modifications, andalternatives.

All of the components in FIG. 13 may be active and operating in parallelto provide redundancy. The ASP points can be rerouting signals based onmonitoring conditions of the system. ASP points can be monitoring anydata associated with the digital domain. In addition to monitoring thepower of the digital signals, the I/Q content of the signal can beanalyzed to determine the quality of the primary feed 118 and/or thesecondary feed 120. Thus, monitoring and analysis of the feeds is notlimited to complete loss of signal (e.g., cutting of primary feed 118),but can include metrics related to the quality of the signals.

FIG. 20 is a block diagram illustrating uplink redundancy according toone embodiment of the present invention showing the basic structure of afull redundancy digital DAS architecture. Multiple uplink primary datastreams are received on the primary fibers 1338 and secondary fibers1340 from the primary and secondary DDUs, respectively. In theillustrated embodiment, the uplink data streams received at the primaryintegrated DAU 1302 from multiple DDUs include a primary data streamcarrying the primary uplink feed for the 700 MHz Band, P1P 2002; aprimary data stream carrying the secondary uplink feed for the 700 MHzBand, P1S 2004; a primary data stream carrying the primary uplink feedfor the 800 MHz Band, P2P 2006; and a primary data stream carrying thesecondary uplink feed for the 800 MHz Band, P2S 2008. Further, theuplink data streams received at the secondary integrated DAU 1304 frommultiple DDUs include a secondary data stream carrying the primaryuplink feed for the 700 MHz Band, S1P 2010; a secondary data streamcarrying the secondary uplink feed for the 700 MHz Band, S1S 2012; asecondary data stream carrying the primary uplink feed for the 800 MHzBand, S2P 2014; and a secondary data stream carrying the secondaryuplink feed for the 800 MHz Band, S2S 2016.

DSP Unit 1312 is configured to implement ASP1 c 2018. ASP1 c 2018 passesa data stream carrying the primary uplink feed by default (P1P 2002, P2P2006, S1P 2010, S2P 2014). ASP1 c 2018 can be configured to monitor thedata stream carrying the primary uplink feed and switch to a data streamcarrying the secondary uplink feed (P1S 2004, P2S 2008, S1S 2012, S2S2016) if loss of primary uplink feed is detected (primary optical pathloss, or primary hdDDU failure) The outputs of ASP1 c can be summed 2024to create a local uplink data stream 2020 and passed to ASP2 b 2022.

The local uplink data stream 2020 is split by the DSP unit 1312 at ASP2b 2022 and a copy of the local uplink data stream 2020 is transmitted tothe secondary integrated DAU 1304. ASP2 b 2022 can include logic thatmonitors the local uplink data stream 2020 and controls the output usinga switch. If a characteristic of the local uplink data stream 2020 doesnot meet a signal or data stream threshold, ASP2 b 2022 can select abackup uplink data stream 2026 from the secondary integrated DAU 1304.In some embodiments, ASP2 b 2022 can receive data related to theintegrity of the local uplink data stream 2020 from ASP1 c 2018. Theuplink data stream output from ASP2 b 2022 is delivered to theappropriate RF section by a splitter/combiner 2028. The uplink datastream is further split at ASP1 a 1326 and ASP1 b 1328 and transmittedto both the 700 MHz primary RF section 1320 and the 700 MHz secondary RFsection 1322 and the 800 MHz primary RF section 1345 and the 800 MHzsecondary RF section 1346 respectively. In some implementations, ASP1 a1326 may receive a status for the redundant RF section and select an RFsection to receive the upstream signal using a switch. The RF Switch (RFSW-PP) 2030 passes a primary RF signal from the primary integrated DAU1302, or switches to an RF signal from the secondary primary integratedDAU 1304 if the primary RF signal is lost. RF SW-SP 2032 passes aprimary RF signal from the secondary integrated DAU 1304, or switches toa secondary RF signal from the primary integrated DAU 1302 if theprimary RF signal is lost. Both RF switches RF signal is deliver the RFsignal to the associated Base Station.

FIG. 14 is a block diagram illustrating DDU 400 fiber (feed) redundancyand aggregation capability according to an embodiment of the presentinvention. In the default mode of operation, the digital distributionunit (DDU) 400 receives the primary digital data stream 418 and thesecondary digital data stream 420 from the primary host unit (primaryDAU 402) and the secondary host unit (Secondary DAU 404) located at theMain Headend 410 location, which can be referred to as the primary datastream 418 and the secondary data stream 420. A main Automated SelectionPoint 3 a (ASP3 a) 1402 passes the primary data stream 418 by default orswitches to the secondary data stream 420 if loss of the primary datastream 418 is detected (e.g., which could result from the primary host(primary DAU 402) failing or failure of the primary fiber optic cable1406 connecting the host and the DDU).

FIG. 14 illustrates local content represented by a primary local datastream 422 and a secondary local data stream 424 from a Local Headend412. Thus, the DDU 1400 has the capability to receive and aggregatelocal content converted to a digital data stream (for example, at the700 MHz or the 800 MHz bands). If local content is present, for example,from a separate municipality represented by the local headend, then alocal ASP3 b 1404 receives the data streams at small form factor port(SFP) 3 and SFP4 and passes the primary local data stream 422 by defaultor switches to the secondary local data stream 424 if loss (e.g.,operation below a threshold) of the primary local data stream 422 isdetected. A combiner 1408 sums the data streams provided by the mainASP3 a 1402 and/or the local ASP3 b 1404 for delivery of aggregated datato the DRUs.

It should be noted that in the implementation illustrated in FIG. 14,both the primary and secondary DDUs have similar functionality. Theprocessing conducted inside the DSP unit 1412 in the DDUs can beremotely updated/reconfigured. The ASP points are rerouting signalsbased on monitoring conditions of the system. ASP points can bemonitoring any data associated with the digital domain. In addition tomonitoring the quality of the digital data streams, the I/Q contentassociated with the signal can be analyzed to determine the quality ofthe primary feed 118 and the secondary feed 120. The logic implementingASP3 can provide switching times in millisecond range.

FIG. 21 is a block diagram illustrating DDU uplink signal redundancy tothe main headend and the local headend feed. The DDU 1400 receives anuplink digital data stream generated by DRUs over a plurality of fiberoptic connections 2102 connected to a plurality of input ports 2104. Theplurality of input ports 2104 are coupled to the DSP unit 1412. In someembodiments, the DSP unit 1412 can include logic that processes theuplink digital data stream generated by the DRUs. The DSP unit 1412includes a summer 2106 that combines the uplink digital data streamscoming from multiple DRUs. Next, the DSP Unit 1412 delivers the uplinkdigital data stream to a splitter 2108 that separates the uplink digitaldata stream into two signals, a first uplink digital data stream 2110for the main headend 410 and a second uplink digital data stream 2112for the local headend 412. The main ASP3 a 1402 splits the first uplinkdigital data stream 2110 for simultaneous transmission over the primaryoptical path 2114 and the secondary optical path 2116 to the MainHeadend. Local ASP3 b 1404 splits the second uplink digital data stream2112 for simultaneous transmission over the primary optical path 2118and the secondary optical path 2120 to the local headend 412.

FIG. 15 is a block diagram illustrating fiber to remote redundancyaccording to an embodiment of the present invention. FIG. 15 illustrateselements of the digital remote unit (DRU) 1500 and redundancy providedat the DRU. The DRU 1500 receives the primary digital data stream 520and the secondary digital data stream 522 from the digital distributionunits primary DDU 510 and secondary DDU 512. The primary digital datastream 520 and the secondary digital data stream 522 are received at aprimary optical port 1512 and a secondary optical port 1514respectively. An Automated Selection Point 4 a (ASP4 a) 1502 passes theprimary digital data stream 520 or switches to the secondary digitaldata stream 522 if loss of primary digital data signal is detected(which could result, for example, from failure of the primary DDU 510 orthe primary fiber optic cable 1504 failing). Similar processing can beperformed for optional bands that are utilized as well as summing asappropriate. The RF sections 1530 translate the digital signal to theanalog domain for subsequent broadcast through the broadcast media,including a leaky coaxial cable or a station antenna, after multiplexingas appropriate.

Implementation of the DSP unit 1524 using an FPGA enables the processingconducted by the DSP unit 1524 to be remotely updated/reconfigured asappropriate. The ASP points are rerouting signals based on monitoringconditions of the system. ASP points can be monitoring any dataassociated with the digital domain. In addition to monitoring thequality of the digital data streams, the I/Q content associated with thesignal can be analyzed to determine the quality of the primary feed 118and the secondary feed 120. Additionally, switching times for the ASP4 a1502 in the DRU 1500 are on the order of the millisecond range.

In FIG. 15 optional primary and secondary data streams 1506 at a second(e.g., 800 MHz) band are illustrated. Thus, the DRU 1500 has thecapability to receive and aggregate content at different bands (forexample, at the 700 MHz or the 800 MHz bands). If the optional band ispresent, for example, from a separate municipality, then a second ASP4 b1510 receives the data streams at SFP3 and SFP4 and passes the primarydata stream in the optional band or switches to the secondary datastream in the optional band if loss of the primary data stream in theoptional band is detected. A combiner 1508 sums the data streamsprovided by the main ASP4 a 1502 and/or optional band second ASP4 b 1510for production of aggregated data at the DRUs.

FIG. 16 is a block diagram illustrating redundancy at a remote unit, DRU1500, through local aggregation according to an embodiment of thepresent invention. FIG. 16 shares similarities with FIG. 15 anddescription provided in relation to FIG. 15 is applicable to FIG. 16 asappropriate. The DRU 1500 has ability to receive and aggregate localcontent converted to a digital data stream 1602 (for example, at the 700MHz or the 800 MHz bands). Thus, the DRU 1500 provides an alternativeapproach for local content aggregation that can supplement or beutilized in place of local content aggregation that is performed at theDDU. Implementation of the DSP unit 1524 using an FPGA enables theprocessing conducted by the DSP unit 1524 to be remotelyupdated/reconfigured as appropriate.

FIG. 16 illustrates local content represented by a primary local datastream 1610 and a secondary local data stream 1612 from a Local Headend1608. Thus, the DRU 1500 has the capability to receive and aggregatelocal content converted to a digital data stream 1602 (for example, atthe 700 MHz or the 800 MHz bands). If local content is present, forexample, from a separate municipality, then the second ASP4 b 1510receives the data streams at SFP3 and SFP4 and passes the primary localdata stream 1610 or switches to the secondary local data stream 1612 ifloss of the primary local data stream 1612 is detected. A combiner 1508sums the data streams provided by the main ASP4 a 1502 and/or the localsecond ASP4 b 1510 for production of aggregated data at the DRUs.

FIG. 22 is a block diagram illustrating DRU uplink signal redundancy toa primary DDU, a secondary DDU and a local headend. DRU 1500 receives RFsignals from an antenna 2202. Signals are processed inside band/channeldedicated RF sections 1530, and then translated to baseband andtransmitted to analog to digital converters (ADCs) 2204. The ADCs 2204convert the baseband signals to an uplink digital data stream and arecoupled to the DSP unit 1524. The DSP unit 1524 sums 2206 the uplinkdigital data streams coming from the ADCs 2204 coupled to the DSP Unit1524. Next, the DSP Unit 1524 delivers the summed uplink digital datastreams 2214 to a splitter 2208 that separates the summed uplink digitaldata streams into two signals, a first uplink digital data stream 2210for the DDUs and a second uplink digital data stream 2212 for the localheadend 1608. The first ASP4 a 1502 splits the first uplink digital datastream 2210 for simultaneous transmission over the primary optical path2216 to the primary DDU 510 and the secondary optical path 2218 to thesecondary DDU 512. The Second ASP3 b 1510 splits the second uplinkdigital data stream 2212 for simultaneous transmission over the primaryoptical path 2220 and the secondary optical path 2222 to the localheadend 1608.

FIG. 17 is a block diagram illustrating redundancy utilizing multipleDRUs according to an embodiment of the present invention. As describedbelow, a redundant DRU 1704 is implemented with integrated dual opticalbypass switches 1706 and RF bypass switches 1708. In someimplementations, the optical bypass switches may be replaced withoptical splitters/combiners. As an alternative to substantiallyoverlapping antenna coverage areas as illustrated in FIG. 7, theimplementation illustrated in FIG. 17 provides redundant DRUs forapplications in which the additional cost of the redundant DRU 1704 isjustified by the additional backup protection provided by the use of theredundant DRU 1704. It should be noted that combinations of thearchitectures in FIGS. 7 and 17 can be implemented in which redundantDRUs are utilized in conjunction with overlapping antenna coverageareas. One of ordinary skill in the art would recognize many variations,modifications, and alternatives.

As illustrated in FIG. 17, the primary DRU 1702 receives the primarydata stream 520 and the secondary data stream 522 from a primary DDU 510and a second DDU 512. In default mode, the primary data stream 520 isprocessed through the DSP unit 1524 in the primary DRU 1702, convertedto an RF signal in the RF section 1710 of the primary DRU 1702, andbroadcast through leaky coaxial cable or a station antenna 1712. Duringnormal operation, the secondary DRU 1704 is active, but does not receivethe primary data stream 520 and the secondary data stream 522, which aredelivered to the primary DRU 1702 by the optical bypass switches (OBSs)1706. During normal operation, the primary DRU 1702 monitors the primarydata stream 520 and the secondary data stream 522, operating using theprimary data stream 520 as a default in some implementations. If theprimary data stream 520 fails, then the primary DRU 1702 can switch tousing the secondary data stream 522 as discussed in relation to ASP4 a1502 of the primary DRU 1702 as discussed in relation to FIGS. 15 and16.

In the event that the primary DRU 1702 fails, the OBSs 1706 and the RFbypass switch (RFBS) 1708 will shift to the bypass position. The OBSs1706 in this bypass position will switch to redirect and/or deliver theprimary data stream 520 and the secondary data stream 522 to thesecondary DRU 1704, which receives them at input ports 1714 coupled tothe automatic selection point 4 a (ASP4 a) 1502 of the secondary DRU1704. In the embodiment illustrated in FIG. 17, the OBSs 1706 areintegrated into the primary DRU 1702 along with the RFBS 1708. Thesecondary DRU RF output 1716 is provided to RFBS 1708, which, in thebypass position, outputs the RF signal received from the secondary DRU1704 rather than the primary DRU RF output 1720 from the multiplexer1718 of the primary DRU 1702. As a result, the secondary DRU RF output1716 is directed to leaky coaxial cable or a station antenna 1712 orother suitable broadcast equipment. Thus, in this mode of operation, theoptical signals will be delivered to the input ports 1714 of thesecondary DRU 1704 and the RF signal from the secondary DRU 1704 will bedelivered to the leaky coaxial cable or station antenna 1712.

FIG. 23 is a block diagram illustrating uplink signal redundancy fromdual redundant DRUs to a primary DDU and a secondary DDU. Primary DRU1702 receives RF signals from an antenna 2302. If the primary DRU 1702is operational, the uplink signals are processed as discussed inrelation to DRU 1500 in FIG. 22. If the primary DRU 1702 fails, RFBS1708 and the OBSs 1706 will switch to the bypass position and the uplinksignals will shift to the secondary DRU 1704.

FIG. 18 is a simplified block diagram according to one embodiment of theinvention showing the basic structure of a full redundancy DigitalPublic Safety Digital DAS architecture 1800. As illustrated in FIG. 18,the architecture 1800 shares some similarities with FIG. 7, thedescription of which is applicable to FIG. 18 as appropriate. Theprimary feed 118 and the secondary feed 120 are split between multiplehosts.

Fiber redundancy between the Main Headend 1802 and the Secondary Headend1804 is provided by a first fiber connection 1806 between the primaryhost 1812 and the primary DDU 1814 as well as a second fiber connection1808 between the secondary host 1816 and the secondary DDU 1818. Forredundancy, a third fiber connection 1810 between the primary DDU 1814and the secondary DDU 1818 is provided. In case of failure of theprimary DDU 1814, the primary/secondary stream provided by the hostunits will be transmitted from the DSP block 1820 of the functioning DDUto the DSP block 1820 of the failed DDU.

In a similar manner, redundancy at the tunnel/station distribution 1822is provided by a fourth fiber connection 1824 between the primary DDU1814 and the primary DRU 1826, a fifth fiber connection 1828 between thesecondary DDU 1818 and the secondary DRU 1830, and a fiber connectionbetween the DSP block 1820 of the primary and secondary DRUs. In case offailure of one of the DRUs, the signal from the working DRU can berouted to the failed DRU for broadcast through the antenna of the failedDRU.

FIG. 19 is a simplified flowchart illustrating a method for selecting aprimary or secondary feed according to an embodiment of the presentinvention. As an example, the method can include processing RF signalsat a DAU. First, the DAU receives a primary RF signal and a secondary RFsignal (1902). The primary and secondary RF signals may be received froma local BTS or a remote BTS over a wired or wireless connection. In someimplementations, the RF signal may be received over the air from aremote BTS. Next, the DAU will translate the primary and the secondaryRF signals to the digital domain (1904). In some implementations, theDAU may use an FPGA to implement an ADC. In other implementations, theDAU may use a separate ADC to translate the primary and secondary RFsignals to the digital domain. The DAU receives the primary RF signal asa digital primary feed and the secondary RF signal as a secondarydigital feed at an automated selection point 1 a (ASP1 a) (1906).

In some implementations, ASP1 a will output the primary feed by default.ASP1 a will determine if the primary feed is above a threshold value(1908). The ASP1 a can monitor digital signal characteristics or analyzethe digitized RF signal to determine a threshold value. ASP1 a outputsthe primary feed if it is above the threshold value (1912). If theprimary feed is below a threshold value, ASP1 a will output thesecondary feed (1910). Next, the output from ASP1 a is combined withother frequency bands present at the DAU (1914).

The combined output can be transmitted to a secondary DAU and a secondASP, ASP2 (1916). The DAU receives a secondary DAU feed at ASP 2 (1918)and ASP2 determines if the primary feed is still above a threshold value(1920). If the primary feed is above a threshold value, ASP2 outputs theprimary feed (1922) for transmission using an optical port. If ASP2determines the primary is below a threshold value, ASP2 outputs thesecondary DAU feed (1924) for transmission using an optical port.

It should be appreciated that the specific steps illustrated in FIG. 19provide a particular method of selecting a primary or secondary feedaccording to an embodiment of the present invention. Other sequences ofsteps may also be performed according to alternative embodiments. Forexample, alternative embodiments of the present invention may performthe steps outlined above in a different order. Moreover, the individualsteps illustrated in FIG. 19 may include multiple sub-steps that may beperformed in various sequences as appropriate to the individual step.Furthermore, additional steps may be added or removed depending on theparticular applications. One of ordinary skill in the art wouldrecognize many variations, modifications, and alternatives.

FIG. 25 is a block diagram according to one embodiment of the presentinvention showing the basic structure of a full redundancy digital DASarchitecture 2500. The architecture 2500 includes an RF Headend 2538that is fed by a combination of a 700 MHz Band BTS 2502 and an 800 MHzBand BTS 2504. The 700 MHz Band BTS 2502 outputs a 700 MHz feed 2516 toa splitter/combiner 2506. The 800 MHz Band BTS 2504 outputs an 800 MHzfeed 2518 to a second splitter/combiner 2520. The splitter/combinerelements create a primary feed and a secondary feed for each frequencyand is coupled to four DAUs, a 700 MHz primary DAU 2508, a 700 MHzsecondary DAU 2510, an 800 MHz primary DAU 2512, and an 800 MHzsecondary DAU 2514.

The 700 MHz primary feed 2522 is received at an input port on the 700MHz primary DAU 2508. As described above, the DAU creates a primarydigital data stream that includes the 700 MHz primary feed 2522. The 700MHz primary DAU 2508 also receives a primary digital data stream fromthe 800 MHz primary DAU 2512 over a first optical fiber connection 2530.The 700 MHz primary DAU 2508 combines the digital data streams asdiscussed above in FIG. 13 and transmits a primary digital data streamover optical fiber connections 2534 to a plurality of DRUs 2536. The 700MHz secondary feed 2524 is received at an input port on the 700 MHzsecondary DAU 2510. As described above, the DAU creates a secondarydigital data stream that includes the 700 MHz secondary feed 2524. The700 MHz secondary DAU 2510 also receives a secondary digital data streamfrom the 800 MHz secondary DAU 2514 over a second optical fiberconnection 2532. The 700 MHz secondary DAU 2510 combines the digitaldata streams as discussed above in FIG. 13 and transmits a secondarydigital data stream over optical fiber connections 2534 to the pluralityof DRUs 2536.

It is also understood that the examples and embodiments described hereinare for illustrative purposes only and that various modifications orchanges in light thereof will be suggested to persons skilled in the artand are to be included within the spirit and purview of this applicationand scope of the appended claims.

Table 1 is a glossary of terms used herein, including acronyms.

TABLE 1 Glossary of Terms ADC Analog to Digital Converter BTS BaseTransceiver Station CDMA Code Division Multiple Access CWDM Coarse WaveDivision Multiplexing DAU Digital Access Unit DDC Digital Down ConverterDDU Digital Distribution Unit DNC Down Converter DRU Digital Remote UnitDSP Digital Signal Processing DUC Digital Up Converter DWDM Dense WaveDivision Multiplexing FPGA Field-Programmable Gate Array PA PowerAmplifier RF Radio Frequency RRH Remote Radio Head RRU Remote Radio HeadUnit UMTS Universal Mobile Telecommunications System WCDMA Wideband CodeDivision Multiple Access WLAN Wireless Local Area Network

What is claimed is:
 1. A redundancy system for data transport in aDistributed Antenna System (DAS), the redundancy system comprising: aplurality of Digital Access Units (DAUs), wherein each of the pluralityof DAUs is fed by a plurality of data streams and is operable totransport digital signals between others of the plurality of DAUs; aplurality of Digital Distribution Units (DDUs), each of the plurality ofDDUs being in communication with each of the plurality of DAUs usingcross connection communication paths; and a plurality of Digital RemoteUnits (DRUs), each of the plurality of DRUs being in communication witheach of the plurality of DDUs using cross connection communicationspaths.
 2. The system of claim 1, wherein the plurality of DAUs areinterconnected.
 3. The system of claim 1, wherein the plurality of DDUsare coupled via at least one of ethernet, optical fiber, microwave lineof sight, a wireless link and/or a satellite link.
 4. The system ofclaim 1, wherein the plurality of DRUs are coupled via at least one ofethernet, optical fiber, microwave line of sight, a wireless link and/ora satellite link.
 5. The system of claim 1, wherein each of theplurality of DDUs communicate with one or more of the plurality of DAUsvia an optical communication path.
 6. The system of claim 1, wherein theplurality of DAUs are connected to one or more base transceiverstations.
 7. The system of claim 1, wherein at least one of theplurality of DAUs are wirelessly connected to one or more basetransceiver stations.
 8. The system of claim 1, wherein at least one ofthe plurality of DAUs are wirelessly connectable to one or more basetransceiver stations.
 9. The system of claim 1, wherein redundancy inthe system is achieved through interconnection of the plurality of DAUs,the plurality of DDUs and the plurality of DRUs.
 10. The system of claim1, wherein redundancy in the system is achieved through opticalinterconnection of the plurality of DAUs, the plurality of DDUs and theplurality of DRUs.
 11. The system of claim 1, wherein the plurality ofDRUs are configured to receive redundant data streams.
 12. The system ofclaim 1, further comprising a local base transceiver station and aremote base transceiver station, the local base transceiver stationbeing configured for a primary feed from an above ground base station,and the remote base transceiver station being configured for an off-airsecondary feed.
 13. The system of claim 1, wherein each of the pluralityof DDUs include one or more optical interfaces.
 14. The system of claim1, further comprising dual fiber links feeding each of the plurality ofDRUs.
 15. A redundant Distributed Antenna System (DAS) comprising: aplurality of Digital Access Units (DAUs), wherein each of the pluralityof DAUs is configured to be fed by a plurality of data streams and isoperable to transport digital signals between others of the plurality ofDAUs; a plurality of Digital Distribution Units (DDUs), each of theplurality of DDUs configured to communicate with each of the pluralityof DAUs using cross connection communication paths; and a plurality ofDigital Remote Units (DRUs), each of the plurality of DRUs configured tocommunicate with each of the plurality of DDUs using cross connectioncommunications paths.
 16. The system of claim 15, wherein the pluralityof DAUs are interconnected.
 17. The system of claim 15, wherein theplurality of DDUs are coupled via at least one of ethernet, opticalfiber, microwave line of sight, a wireless link and/or a satellite link.18. The system of claim 15, wherein the plurality of DR Us are coupledvia at least one of ethernet, optical fiber, microwave line of sight, awireless link and/or a satellite link.
 19. The system of claim 15,wherein each of the plurality of DDUs communicate with one or more ofthe plurality of DAUs via an optical communication path.
 20. The systemof claim 15, wherein the plurality of DAUs are connected to one or morebase transceiver stations.
 21. The system of claim 15, wherein at leastone of the plurality of DAUs are wirelessly connected to one or morebase transceiver stations.
 22. The system of claim 15, wherein at leastone of the plurality of DAUs are wirelessly connectable to one or morebase transceiver stations.